Miller-Fisher syndrome (MFS) is a rare variant of Guillain-Barré syndrome (GBS) manifesting as the triad of ataxia, areflexia, and ophthalmoplegia. With the extensive 2019 coronavirus disease (COVID-19) immunization program, cases of GBS or MFS following vaccination are increasingly being reported. A 64-y-old Chinese man presented with new-onset paresthesia of the extremities, bilateral abduction limitation, right facial palsy, areflexia of bilateral lower limbs, and left-dominant limb ataxia 12 d after the second dose of inactivated vaccine against COVID-19. Cerebrospinal fluid analysis indicated albumin-cytological dissociation and was positive for anti-GQ1b IgG and anti-GT1b IgG. Nerve conduction studies of limbs showed evidence of axonal neuropathy with reduced sensory amplitudes. Based on the clinical presentations, temporal progression of symptoms, and laboratory findings, the diagnosis of MFS-GBS overlap syndrome was made. The patient was treated with intravenous immunoglobulin and acupuncture and made a complete recovery 54 d after the onset of his initial neurological signs. To the best of our knowledge, we report the first case of MFS-GBS overlap syndrome following the inactivated COVID-19 vaccination. However, a coincidental relationship with this inactivated vaccine cannot be excluded. Although the benefits of COVID-19 vaccination largely outweigh its risk and the prognosis of MFS is generally favorable, a close surveillance of neurological complications post-COVID-19 vaccination is always necessary, considering its potentially disabling and lethal effects on vaccinated populations.